1. Field of the Invention
The present invention relates to mixtures of catenate alkoxysiloxanes of the general formula R3SiOxe2x80x94(SiR2xe2x80x94O)mSiR3 and also cyclic alkoxysiloxanes of the general formula 
said alkoxysiloxanes also being referred to below for short as siloxanes or siloxane oligomers, a process for preparing said mixtures and to their use.
2. Discussion of the Background
Organofunctional/vinyl-functional alkoxysiloxanes are used, for example, as crosslinkers for thermoplastic polyolefins. The performance requirements imposed on such products are nowadays very high and there is a pressing need for specially tailored solutions.
It is known that a 1,3 divinyltetramethoxydisiloxane contaminated with higher polymers can be obtained during the distillative workup of crude vinyltrimethoxysilane as obtained in the reaction of vinyltrichlorosilane and methanol (Nagel et al., Journal of Organic Chemistry, Volume XVI (1951), Part 2, 1768-1771).
EP 0 518 057 A1 discloses a process for preparing such mixtures of catenate and cyclic siloxane oligomers. In that process, corresponding organoalkoxysilanes with different substituents are subjected to controlled hydrolysis, condensation or cocondensation with addition of HCl catalyst and a defined amount of water, the catalyst and the free alcohol being removed from the product mixture following the reaction. Where alkoxysilanes with different organic functional groups are used, the desired aim is to obtain a distribution of the different substituents in the resultant siloxane oligomers which is very uniform, i.e., random. The aim in this case is for a molar ratio of vinyl to alkoxy substituents of from 1:1 to 1:8 and a molar ratio of vinyl to alkyl substituents of from 1:0 to 1:8, with not more than one vinyl substituent occurring in the siloxane per silicon atom.
Moreover, EP 1 205 505 A2 discloses a continuous process for preparing a mixture of catenate and cyclic organoalkoxysiloxanes starting from corresponding organochlorosilanes.
All of this is difficult to control, since hydrolyzable organosilanes which carry different organic functional groups are known to possess markedly different hydrolysis and condensation behaviors. Furthermore, organoalkoxysilanes are expensive raw materials.
One object of the present invention to provide a process for preparing organofunctional alkoxysiloxane mixtures, especially vinyl-functional or alkyl/vinyl-functional and/or corresponding aryl-functional alkoxysiloxanes.
This and other objects have been achieved by the present invention, the first embodiment of which provides a process for preparing a mixture, which mixture includes catenate and cyclic siloxanes of formula I
R3Sixe2x80x94Oxe2x80x94(SiR2xe2x80x94Oxe2x80x94)mSiR3xe2x80x83xe2x80x83(I)
and cyclic siloxanes of formula II 
wherein m is an integer from 0 to 40 and n is an integer from 2 to 40,
wherein R2 and R3 are each independently an organic functional group selected from the group including alkyl, aryl, vinyl, and alkoxy groups,
and wherein there is not more than one vinyl group or aryl group per silicon atom,
said process including a controlled hydrolysis, condensation or cocondensation reaction of at least one monomeric silane in alcoholic solution in the presence of an acidic catalyst, which reaction includes contacting alcohol, water, and at least one chlorosilane component selected from the group including (i), (ii), (iii):
(i) at least one arylchlorosilane;
(ii) at least one admixture selected from the group including alkylchlorosilane and arylchlorosilane, arylchlorosilane and vinylchlorosilane, alkylchlorosilane and vinylchlorosilane, and arylchlorosilane and vinylchlorosilane and alkylchlorosilane;
(iii) at least one selected from the group including chlorosilane, alkylchlorosilane, arylchlorosilane, and vinylchlorosilane in two or more separate batches to obtain two or more separate mixtures and thereafter combining the mixtures;
to form the mixture of the catenate and cyclic siloxanes.
Another embodiment of the invention provides a mixture, prepared according the above process.
Another embodiment of the invention provides an alkyl-functional, vinyl-functional, aryl-functional, alkyl/vinyl-functional, alkyl/aryl-functional, aryl/vinyl-functional and/or alkyl/aryl/vinyl-functional alkoxysiloxane mixture or blend thereof, prepared according to the above process.